The invention relates to a tape pad support assembly for use in a magnetic tape cassette, in particular, of a miniature size which is used in a miniature cassette tape recorder.
As is well known, a tape pad support assembly in a magnetic tape cassette comprises a leaf spring which is disposed so as to extend on the rear side of a portion of a magnetic tape which extends along a plurality of window slots formed in the front end face of a tape cassette, thereby serving to urge the magnetic tape against a magnetic head or heads which are inserted into the cassette through the window slot or slots.
The construction of a conventional pad support spring is illustrated in FIGS. 1 and 2. FIG. 1 shows a plan view of a cassette half 2, in particular, of a micro-cassette type, in which a pad support spring 1 is mounted. The cassette internally houses a pair of tape supply and take-up hubs 3, 4 which are rotatably mounted therein. A magnetic tape T has its one end secured to the hub 3 and then disposed thereon by being spirally wound thereon. Subsequently, the tape is guided by a pair of guide rollers 5, 6 so as to extend in a taut condition along a plurality of window slots 2a, 2b and 2c which are formed in the front end face of a cassette, and its opposite end is anchored to the other tape hub 4. The window slot 2a is adapted to receive a pinch roller while the remaining window slots 2b, 2c are adapted to receive magnetic heads.
The pad support spring 1 is disposed on the back side of a portion Ta of the tape which extends along the front end face of the cassette, and extends parallel to the direction of tape running. The spring is formed of a very thin resilient sheet material, and is disposed so that its plane is in parallel relationship with the surface of the tape portion Ta. The leaf spring has a central portion 1a which is retracted inward into the cassette in a channel configuration in order to avoid any interference with a capstan aperture 12 which is located in the cassette in alignment with the central window slot 2a. A projection 1b is centrally formed on the leaf spring and extends inward into the cassette to bear against a spring abutment 7 which is integrally formed with the cassette half 2. A pair of tabs 1c, 1d extend in the same direction as the projection 16 on the opposite sides thereof to engage the opposite lateral sides of the abutment 7, thereby preventing an axial displacement of the spring in the direction of arrows A.sub.1.
A pair of pads 8, 9 are adhesively mounted on a pair of end portions 1e, 1f of the spring so as to be in alignment with the respective slots 2b, 2c. As shown in FIG. 2, the free ends 1g, 1h of the spring have a reduced width, and bear against a pair of stop pins 10, 11 (see FIG. 1), thereby controlling the resilience which acts in a direction toward the tape portion Ta.
Considering the operation of the leaf spring, it is diagrammatically shown in FIGS. 3(a)-3(c). In a single head system, a magnetic head 14 is inserted through one of the window slots toward one of the pads, for example, pad 8 as illustrated in FIG. 3(b). When the tape cassette is removed and inverted upside down, the same head 14 will be advanced toward the other pad 9. In each of these instances, the pads 8, 9 urge the magnetic tape portion Ta against the surface of the magnetic head 14.
In a two head system in which a pair of magnetic heads 16, 17 which may be a combination of a record/playback head and an erase head, for example, are advanced through the window slots toward the pads 8, 9 so that they move into abutting relationship with the tape portion Ta, as shown in FIG. 3(c), the illustrated pad support spring 1 exhibits a poor response. Specifically, if both heads 16, 17 are simultaneously advanced into contact with the tape Ta, the resilience of spring 1 will act relatively uniformly through the both pads 8, 9. However, it is very difficult, if not impossible, to bring both heads into engagement with the tape portion Ta simultaneously, and usually one of the heads will precede the other in engaging with the spring through the associated pad. As illustrated in FIG. 3(b), the spring 1 will rotate counter-clockwise about the fulcrum 1b so that the other head which lags in engaging with the tape will be subjected to an increased resilience of the spring which results from the counter-clockwise rotation thereof, resulting in an unbalanced contact pressure between the respective heads and the tape. This means that the magnetic head which lags in engaging with the tape must be advanced with an increased force. It will be also appreciated that the above disadvantage will be even more aggravated if the projection 1b which defines the fulcrum of the spring 1 has a larger dimension.
Another consideration to be paid with respect to the head and support arrangement is the fact that a magnetic head is not always advanced into the cassette in a horizontal plane, but may be advanced with an angle of inclination with respect to the horizontal, as illustrated in FIG. 4. When a head 14 assumes a skewed position when it is being inserted, the tape portion Ta and the associated pad, for example, pad 8, will be pressed in a corresponding manner to assume a skewed position. Since the spring 1 comprises a one-piece leaf spring, a skewed position of one free end 1e will be transmitted to the other free end 1f, resulting in a skewed position of the other pad 9. If the other head is inserted in a horizontal plane under this condition, the tape will engage this head in a skewed position into which it is forced by the associated pad, thus resulting in a failure to achieve close contact between the tape and the head surface and also causing a strain to be produced in the tape.
The described pad support assembly has a further disadvantage in that the fulcrum of the spring 1 is formed by the tip of the projection 1b extending rearwardly from the spring and thus is situated at a rearwardly retracted position relative to the spring 1, the distance between the pad and the fulcrum is increased and the pad cannot respond immediately, resulting in a poor response of the pad as the magnetic head or heads are being advanced into the associated window slots. To remove this difficulty, it is desirable that the distance between the fulcrum of the spring and the pad be minimized.